Beijing: map of z value
Deciles of z value:
(-0.642, -0.401)
(-0.401, -0.101)
(-0.101, 0.065)
(0.065, 0.167)
(0.167, 0.41)
(0.41, 0.625)
(0.625, 0.729)
(0.729, 0.856)
(0.856, 1.001)
(1.001, 1.213)